1. The Ground Beneath Our Feet
From Bedrock to Soil
Chapter 10: Section 3

2. Section Vocabulary
Soil: a loose mixture of rock fragments, organic material, water, and air that can support the growth of vegetation
Parent Rock: a rock formation that is the source of soil
Bedrock: the layer of rock beneath the soil
Soil Texture: the soil quality that is based on the proportions of soil particles
Soil Structure: the arrangement of soil particles

3. Section Vocabulary (cont)
Humus: dark, organic material formed from the decayed remains of plants and animals
Leeching: the removal of substances that can be dissolved from rock, ore, or layers of soil due to the passing of water

4. What Makes Up Healthy Soil?
Mineral fragments, humus, air, water, and living things
Plant roots, Insects, Worms
Humus
Organic (living) material formed from the decayed remains of plants and animals
Can support the growth of vegetation
Parent rock
A rock formation that is the source of mineral fragments in the soil

5. Go to this link to watch and listen to the difference in residual and transported soils:

6. Soil Formation Soil starts out as rock
The surface rocks break down into smaller pieces and is mixed with organic matter.
Over time this creates a thin layer of soil.
Decaying matter makes the soil thick and rich

8. Soil Texture
Soil Texture ~ the soil’s quality is based on the proportions of soil particles.
Soil texture affects:
Consistency:
soil’s ability to be broken up.
Infiltration:
ability of water to move through soil.

9. Sizes of Weathered Rock That Make Up Soil

10. Different Types of Soil
Every soil type is a mixture of sand, silt, clay.
The right mixture is called loam.
Loam =
40% sand
40 % silt
20 % clay

11. Soil Horizon Link to animation of soil horizon formation:

12. Soil Horizon Each soil profile (horizon) is different from another.
Soil often ends up in a series of layers called horizons:
Humus rich soil at the top
Sediment below hummus
Bedrock on the bottom

13. Soil Horizon O Litter from dead plants and animals A Topsoil E
Zone of intense leaching. B
Collects dissolved substances from upper horizons C
Weathered bedrock R
Bedrock

14. Soil pH Soils can be acidic or basic
pH scale is used to measure how acidic/basic
Measuring pH levels:
Range: 0 – 14;
7 = neutral
Soil below 7 = acidic
Soil above 7 = basic

15. Soil pH
Carbonic acid and Humic acid changed the pH of the soil to be more acidic.
Carbonic acid
come from Carbon Dioxide.
Humic acid
various organic acids produced from humus.

16. Soil and Climate Soil types vary from place to place
Different climates have different types of soil, depending on the temperature and rainfall.
This link describes how climates affects soil:

17. Tropical Climate
Climate = humid air, large amounts of rainfall, warm temperatures
Rich humus because the warmer soils allows dead plants and animals to decay easily.
However, soils are nutrient poor because very thin topsoil layer
Heavy rains leach precious nutrients from topsoil.
Plants demand a lot of nutrients from the soils.

18. Desert Climate
Climate = less than 25 cm rain a year. This lack of rain causes low rates of weathering and ability to support plant and animal life
Slow rate of weathering = Slow rate of soil formation.
Due to no water, salt gathers in the ground.
Salt is toxic to plants!

19. Temperate Climate
Temperate areas get enough rain to cause a high level of chemical weathering
Lots of weathering = lots of fertile soil
Most productive soil in the world, nickname = “breadbasket”
Most of Continental USA has a temperate climate.

20. Arctic Climate
Very cold desert = Slow rate of soil formation because chemical weathering occurs slowly
Low amount of humus due to cold soil temperatures.
Cold temperatures
slow down
decomposition which limits available nutrients.

21. On a separate sheet of paper:
Write your name, date, class color
Number your paper 1 – 10
Answer the next ten following questions:
Write the question and your answer.
Turn in when completed

22. Review Questions 1. What is loam?
A. Loam is the perfect combination of sand, silt, and clay.
B. Loam is the combination of 30% sand, 40% mud, and 30% clay.
C. Loam is located on in horizon B.
D. Loam is the particle quality of any soil.

23. Review Questions
2. Because of the way soil forms, soil often ends up in a series of horizontal layers called ______________________

24. Review Questions 3. How does soil texture affect soil consistency?
A. It has nothing to do with it.
B. Allows water to pass through it easier.
C. The soil’s ability to allow farmers to manipulate it.
D. Allows for plants to grow easily.

25. Review Questions
4. What is the organic material formed in soil from the decayed remains of plants and animals called? - A. Bedrock - B. Parent rock - C. Residual soil - D. Hummus

26. Review Questions
5. Which particle is the biggest one that goes in soil?
A. Clay
B. Silt
C. Quartz
D. Sand

27. Review Questions 6. What acids can change the pH of the soil?
A. Humic acid and Hydrochloric acid
B. Carbonic acid and Humic acid
C. Carbonic acid and water
D. Water and citric acid

28. Review Questions
7. Which climate is called the “breadbasket of the world”?
A. Tropical
B. Desert
C. Temperate
D. Arctic

29. Review Questions
8. What is the difference between residual and transported soils?

30. Review Questions
9. Climate with enough rain to cause a high level of chemical weathering, but not so much that the nutrients are leached out of the soil is ________________________.

31. Review Questions
10. What do we call the removal of substances from soil due to water passing through it? - A. Wedging - B. Infiltration - C. Erosion - D. Leaching